Abstract
Anabaena sp. grew with mono- and di-ester phosphate compounds as sources of phosphate, indicating the presence of phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities. Cell-bound PMEase and PDEase activities were detected during growth in 0.5 and 10 mg PO4l(-1) only when the cellular phosphate concentration fell to 0.46% of cell protein and the activities increased as cellular phosphate content decreased. The Km values for these enzymes were 0.3MM forp-nitrophenyl phosphate and 0.2MM for bis-p-nitrophenyl phosphate, respectively. Only PMEase activity was found extracellularly. The pH optima for PMEase and PDEase were 10.2 and 10.4, respectively, and the temperature optima at pH 10.2 were 37°C and 40°C, respectively. Ca(2+) increased the enzyme activities while Zn(2+) caused marked inhibition. The inorganic phosphate repressed the cellular PMEase activity after a lag of 4 h.
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